New cut angle quartz crystal microbalance with low frequency-temperature coefficients in an aqueous phase

In a traditional quartz crystal microbalance (QCM), an AT-cut (cut angle phi = 35.25 degrees in yxl orientation) quartz wafer is employed because it has low frequency-temperature coefficients (dF/dT) at room temperature region. But when a QCM is in contact with a liquid phase, its frequency is also related to the properties of the liquid, which are temperature dependent. The value of dF/dT is about 20 Hz/degrees C for a 9 MHz AT-cut QCM with one side facing water. In this work, a group of QCMs in new cut angles were prepared. The influence of the cut angle on the frequency-temperature characteristic, response sensitivities to surface mass loading and viscodensity of liquid were investigated. An intrinsically temperature-compensated QCM sensor that possesses low dF/dT values in aqueous solution was reported. When a 9 MHz QCM with phi = 35.65 degrees was contacted with water with one side, its dF/dT value is close to zero at ca. 25 degrees C and its averaged value of |dF/dT| is only 0.6 Hz/degrees C in the temperature range of 23-27 degrees C. The frequency responses to surface mass loading and viscodensity of liquid phase are very close among the QCMs with the cut angles in the range of 35.15-35.7 degrees. The intrinsically temperature-compensated QCM was applied to investigate the alternate adsorption processes of cationic polyelectrolyte and silica nanoparticle. (C) 2008 Elsevier B.V. All rights reserved.